Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper.

In a large skillet, heat the olive oil over medium heat. Add the chopped onion and cook until softened and translucent, about 5-7 minutes. Add the minced garlic and cook for another minute until fragrant.

In a large mixing bowl, combine the thoroughly squeezed dry spinach, crumbled feta cheese, chopped dill, chopped parsley, beaten eggs, black pepper, and nutmeg (if using). Add the cooked onion and garlic mixture to the bowl. Stir everything together until well combined. Taste and adjust seasoning if needed.

Carefully unroll the thawed phyllo dough. Keep the sheets covered with a slightly damp kitchen towel while you work to prevent them from drying out.

Lay one sheet of phyllo dough on your work surface. Lightly brush the entire surface with melted butter or olive oil. Top with another sheet of phyllo dough and brush it with butter/oil. Repeat this process until you have a stack of 4-6 layers.

Cut the stacked phyllo sheets lengthwise into three equal strips.

Place about 1-2 tablespoons of the spinach and feta filling at one end of each strip. Fold the phyllo strip over the filling to create a triangle, like you're folding a flag. Continue folding in a triangular motion up the strip until you reach the end. Brush the outside of each triangle with melted butter/oil.

Place the finished triangles seam-side down on the prepared baking sheet.

Repeat the layering, cutting, filling, and folding process with the remaining phyllo dough, filling, and butter/oil until all the ingredients are used.

Bake for 20-25 minutes, or until the triangles are golden brown and crispy. Let them cool slightly on the baking sheet before serving.